While screening mammography in controlled trials is capable of decreasing breast cancer mortality by 30%, its effectiveness, Costs, and utilization in rural and ethnically diverse Communities is not known. We propose to create a geographically defined, population-based resource in the state of New Mexico, a multi-ethnic and largely rural state. The resource will include complete ascertainment of screening mammograms, breast cancers, and benign breast tumors, and a population-based survey of breast cancer risk factors and screening behaviors in screened and unscreened women. This resource will allow analytic and descriptive studies of the following aspects of screening mammography: 1) differences in outcomes, performance, and utilization in rural vs. urban and among different ethnic populations, 2) radiologic, pathologic and molecular differences in cancers detected by screening and cancers missed by screening, 3) screening costs in the region's largest HMO, including costs of subsequent treatment as a function of stage at diagnosis, and 4) an intervention project using lay health advisors to increase screening rates in a rural and largely Hispanic region in northern New Mexico. The core of the proposed study is the expansion of the Albuquerque metropolitan area surveillance system (established as a pilot study by the New Mexico Tumor Registry in 1990) to include complete coverage of the state's rural areas. This resource consists of mammogram data, benign breast biopsy data, and incident breast cancer data. Linkage of these three data bases allows calculation of mammography sensitivity, positive predictive value, and stage at diagnosis distribution of mammography- detected cancers. We propose to collect electronic data on all mammograms performed in the state of New Mexico, data on all benign and malignant breast biopsies, and data on quality assurance and image quality for radiology groups. Surveillance data for the entire population of women at risk for breast cancer will be augmented by a population-based telephone survey concerning screening knowledge, attitudes, and behaviors that will include women who are and who are not undergoing screening mammography. This resource will provide a unique opportunity to examine screening mammography performance in Hispanics, American Indians, and non-Hispanic whites residing in rural and underserved populations.